Angiography is the medical imaging technique used to visualize the lumen of the blood vessels and organs of the body, including the arteries and veins. Three-dimensional (3D) angiography includes a family of techniques achievable by imaging modalities such as magnetic resonance, computed tomography, ultrasound, and cone-beam X-ray imaging. A 3D angiographic image presents a wealth of information on normal and pathological vessel morphology. These 3D images are used in the diagnosis of vascular abnormalities, disease quantification, treatment planning, and guidance during interventional medical procedures.
Diseases which induce changes in the shape of blood vessels include atherosclerosis, aneurysms, and arterio-venous malformations including fistulas. Atherosclerosis is a disease which is characterized by the deposition of fatty materials, such as cholesterol, and calcium (at more advanced stages or the disease) on the inside surface of the artery wall. Atherosclerosis is also associated with stenosis (i.e. blood vessel narrowing) both locally and in downstream branches of a person's vascular structure. An aneurysm is a pathological bulge or dilatation of the blood vessel wall, which may lead to blood vessel rupture and internal bleeding. Arterio-venous malformations, including fistulas, are abnormal connections or shunts between the arterial and the venous blood vessels, without the normal intervening bed of blood capillaries.
To detect, diagnose, and treat blood vessel pathologies, physicians and other healthcare professionals rely on the visual examination of 3D angiography images and multiple 2D projection or cross sectional images (also known as angiograms). Recent advances in the medical image processing field have made available some software tools for semi-automated quantification of vascular diseases. Software tools for semi-automated quantification of the severity of blood vessel stenosis, and the size of aneurysms are available for use today on some clinical image processing workstations. These tools typically analyze blood vessels through an idealized model of a blood vessel, such as a tubular model with possible branching. One of general steps necessary for analyzing the shape of blood vessels is the extraction of the centerline of these vessels. For diseases like aneurysms or stenosis, the profile of the blood vessel diameter along the centerline abnormally expands or shrinks, respectively. Therefore, the diameter profile may be used to isolate the diseased portion of the blood vessel, and to quantify the severity of the disease. Importantly, the sensitivity of the approach used for analyzing the blood vessel abnormality depends on the initial step of centerline extraction. In addition, such analysis approaches can only result in a limited number of quantitative measures (e.g., area narrowing percentage in the case of stenosis) that are used to document the severity of the disease. In the case of diseases like aneurysms, it is often difficult to completely isolate the aneurysm from the blood vessel automatically, and a high degree of manual interaction is often necessary.
Thus, there is need for a standardized way of examining blood vessel surfaces by clinicians and researchers and for more effective ways of extracting the centerline of the blood vessels, and isolating diseases like aneurysms and stenosis during image processing of a patient's vascular structure.
More broadly, there is also a need for the processing of 3D images of blood vessels to more effectively enable the analysis of the shape of blood vessels of a person, the statistical analysis of the shape and properties of blood vessels in a group of individuals, and the detection and quantification of blood vessel diseases.